How do I select and change a text?
If the Tab key for some reason doesn't put you in Edit Mode, try changing into edit mode using the dropdown menu:



You can find more information about text editing in the manual: http://www.blender.org/manual/modeling/texts/introduction.html#editing-text

Also, if you are a new user and do not have special reasons, there is no point in using an older version. Try the latest release, it's faster and has more features.